Automatic clearance pockets for compressors



A ril 9, 1963 s. 5. SMITH AUTOMATIC CLEARANCE POCKETS FOR COMPRESSORS INVENTOR. @0426; 5 5/):4

BY Parker 4? [Zrzer Jff/O/Y//i R33. ww

Filed Sept. 7, 1960 QQMMmNRSGw United States Patent 3,084,847 AUTGMATIC CLEARANCE POCKETS FOR CUMPRESSORS Sydney 5. Smith, Scarsdale, N.Y., assignor to Nordberg Manufacturing Company, Milwaukee, Wis, a corporation of Wisconsin Filed Sept. 7, 1960, Ser. No. 54,408 2 Claims. (Cl. 230-411.)

This invention is concerned with an engine driven compressor and is in the nature of a control system for an engine-compressor set which keeps the horsepower on the engine constant.

A primary object of my invention is a clearance pocket control for an engine driven compressor which fully protects the engine.

Another object is a simplified control for the clearance pocket of a double acting compressor.

Another object is a clearance pocket control for an engine compressor set which guarantees maximum volumetric efficiency of the engine.

Other objects will appear from time to time in the ensuing specification and drawings in which I illustrate a schematic or diagrammatic layout of my system.

In the drawing, an engine is indicated generally at 10 driving a compressor 12 through a suitable drive or coupling 14. The compressor may be considered to be a double acting unit although certain features or aspects of the invention may be applied as well to a single acting unit. In any event, each side of the compressor has a clearance pocket, indicated at 16 and 18, which communicates freely with the cylinder. I provide a free piston 20 and 22 in each clearance pocket which may move back and forth to vary the volume of the clearance pocket open to the cylinder.

A source of hydraulic fluid, indicated generally at 24, is connected to a suitable pump 26 which supplies fluid through an inlet line 28 to the clearance pockets behind the free piston. Each of the inlets has a check valve, as at 30 and 32, to prevent return flow of the fluid.

I exhaust fluid from the clearance pockets by a suitable outlet line 34 through a valve 36. Each of the outlet lines for each pocket has a check valve, as at 38 and 40, to prevent return flow. The fluid passes through a suitable cooler 42, if desired, before it returns to the supply tank 24.

The governor 44 on the engine may have a control 46 which is suitably connected at 48 to operate the pump. The valve 36 is preferably a solenoid control valve and a suitable connection 50 from the governor control also operates this valve.

The use, operation and function of my invention are as follows:

I provide a variable volume clearance pocket connected to the cylinder of a compressor and depending upon the load involved I enlarge or reduce the volume of the clearance pocket available to the compressor. I Want to keep constant load on the engine, and since the engine is driving the compressor, this requires that I have constant load on the compressor. But from time to time the line load on the compressor will vary depending upon whether the pressure to the compressor increases or decreases. By moving the free piston back and forth in the clearance pocket, I keep the load constant on the compressor and, therefore, the load on the engine is constant. For example, if the discharge line pressure from the compressor increases, this tends to increase the load on the compressor. Therefore, I increase the clearance pocket volume to reduce the load on the engine. The reverse is also true. If the discharge line pressure from the compressor drops, I move the free piston in so that the available volume in the clearance p 3,084,847 Patented Apr. 9, 1953 2 pocket will be reduced and the load on the compressor and engine will stay the same.

In the arrangement shown, the governor control on the engine alternately and intermittently operates the pump and the solenoid control valve. It operates the pump to supply fluid to the clearance pockets to reduce their volume and the solenoid control valve to let fluid out of the clearance pockets to increase their volume. Thus, as load increases due to increased discharge line pressure from the compressor, the governor control will open the solenoid valve to bleed fluid out of the clearance pockets and increase the volume available to the compressor. As the discharge line pressure from the compressor drops, thereby reducing the load on the compressor, the governor control will operate the pump to supply more fluid behind the free pistons, thereby reducing the clearance pocket volume and increasing the load on the compressor and engine.

The check valves on the inlet and outlet prevent reverse flow and, in a double acting compressor, keep both sides in balance. Also, in a double acting compressor the check valves will prevent the hydraulic fluid from racing back and forth which would cause it to heat up tremendously.

An advantage of such an arrangement on a pipeline having a number of stations is that each station will automatically adjust to what the stations on each side of it are doing. Each engine would be operating at maximum volumetric efiiciency and the system completely ignores the suction and discharge pressures. I do this by directly relating the volume of the clearance pocket to the horsepower on the engine. I have shown the control tied to the engine governor but it might be tied to any load factor on the engine.

While I have shown and described the preferred form of my invention, it should be understood that numerous additional modifications, changes, substitutions and alterations may be made without departing from the inventions fundamental theme. I, therefore, wish that the invention be unrestricted, except as by the appended claims.

I claim:

1. In an engine driven compressor, a cylinder and piston, a clearance pocket in communication with the cylinder, a free piston in the clearance pocket having two sides, one side in communication with the cylinder, and means for supplying and exhausting hydraulic fluid from the other side of the piston in the clearance pocket to move the free piston back and forth, including a source of fluid, a pump connected to draw fluid from the source and to supply it to the clearance pocket on the other side of the free piston, an outlet for fluid in the clearance pocket on the other side of the piston, a valve controlling the outlet, and an engine load responsive control alternately energizing either the pump or the valve so that fluid will either be supplied to or exhausted from the other side of the piston, depending upon the load on the engine.

2. In a double acting engine driven compressor, a cylinder and piston, clearance pockets at each end of the cylinder and a free piston in each pocket, means for supplying and exhausting hydraulic fluid from behind the free pistons to vary the volume of the clearance pockets in communication with the cylinder, including an inlet line and an outlet line connected to each clearance pocket behind its free piston, check valves in the inlet and outlet lines to the clearance pockets to prevent reverse flow at all times, a source of fluid, a pump connected to draw fluid from the source and supply it to the inlet line, a control valve in the outlet line, and a load responsive control constructed and arranged to alternately energize either the pump or the control valve so that fluid will either be supplied to or exhausted from engine.

References Cited in the fi1e of this patent UNITED STATES PATENTS Enzinger Oct. 22, 1901 Massa Feb. 16, 1909 4 Riesner Nov. 24, 1931 Moody Dec. 25, 1934 Saharofi Apr. 16, 1940 Condit Nov. 4, 1941 Scheerer May 6, 1958 Crooks Sept. 30, 1958 McGrath Nov. 17, 1959 

2. IN A DOUBLE ACTING ENGINE DRIVEN COMPRESSOR, A CYLINDER AND PISTON, CLEARANCE POCKETS AT EACH END OF THE CYLINDER AND A FREE PISTON IN EACH POCKET, MEANS FOR SUPPLYING AND EXHAUSTING HYDRAULIC FLUID FROM BEHIND THE FREE PISTONS TO VARY THE VOLUME OF THE CLEARANCE POCKETS IN COMMUNICATION WITH THE CYLINDER, INCLUDING AN INLET LINE AND AN OUTLET LINE CONNECTED TO EACH CLEARANCE POCKET BEHIND ITS FREE PISTON, CHECK VALVES IN THE INLET AND OUTLET LINES TO THE CLEARANCE POCKETS TO PREVENT 